Limbic system Flashcards
What is Kluver-Bucy syndrome?
Bilateral lesions of the amygdala (/ medial temporal lobes) resulting in hyperorality (inserting inappropriate objects in the mouth), dietary changes, lack of emotional expression (fear or anger) and hypersexuality
What is Korsakoff’s Psychosis?
Degeneration of the mammillary bodies caused by vitamin B1 (thiamine) deficiency as a result of chronic alcohol use.
Associated with anterograde amnesia, confabulation and hallucinations
What are the functions of the limbic system?
Sensation and perception of emotions
Visceral response to emotions
Memory formation and consolidation
What are the cortical components of the limbic system?
Hippocampus Insula Cingulate gyrus Entorhinal cortex Fornix
What is the function of the hippocampus?
Memory formation and consolidation
What is the function of the insula?
Sets the threshold for emotional responses
What is the function of the cingulate gyrus?
Involved in linking sight and smell to memories and previous emotions
What is the function of the entorhinal cortex?
Interface between the hippocampus and the cortex
What is the function of the fornix?
White matter tract connecting other structures of the limbic system
[Nb. transection of fornix is linked to memory loss]
What are the subcortical components of the limbic system?
Amygdala Mammillary bodies Hypothalamus Olfactory bulb Nucleus Accumbens Anterior thalamus Septal nuclei
What is the function of the amygdala?
“Emotional Centre” - involved in evaluating the emotional valence of situations
What is the function of the mammillary bodies?
Part of the hypothalamus - role in memory
What is the function of the hypothalamus?
Forms connections with multiple nuclei and structures to regulate autonomics, endocrine function and behaviour
What is the function of the olfactory bulb?
Processes olfactory input
What is the function of the nucleus accumbens?
Central to the reward system, reinforcing pleasant experiences
What is the function of the anterior thalamus?
Role in modulating alertness, learning and memory
What is the function of the septal nuclei?
Pleasure (sexual/ orgasm sensation)
What is Papez’s circuit?
Neural circuit central to the limbic system, which is hypothesised to be the basis of emotion/ perception of emotion
What is the pathway of the Papez circuit?
Hippocampus -> Fornix -> Mammillary body -> Mammillothalamic fibres -> Thalamus (anterior nucleus) -> Cingulum -> Entorhinal cortex -> Hippocampus
What is the difference between working and long term memory?
Working = temporary retention (e.g. phone number recall)
Long term = lasts indefinitely
What is the difference between episodic and semantic memory?
Episodic = events (esp. autobiographical) Semantic = facts
What is the difference between declarative and non-declarative (procedural) memory?
Declarative = conscious recollection of knowledge (can be episodic or semantic in nature)
Non-declarative (procedural) = learned skills - can be motor (e.g. riding a bike) or language
How would someone with hippocampal damage present clinically?
Anterograde amnesia (inability to form new memories)
How would someone with damage to the cingulate gyrus present?
Autonomic dysregulation
Emotional disturbances
What additional symptoms would someone with Wernicke-Korsakoff’s Syndrome present with compared to someone with Korsakoff’s Psychosis?
Ataxia
Ophthalmoplegia
Confusion
